This invention relates to an airbag device, which is a protecting device for a seat occupant of a vehicle or the like.
An airbag device is, in general, composed of a casing arranged at the front part in the indoor room of a vehicle such as an instrument panel or a center of a steering wheel, an airbag housed in the casing in a folded fashion, and an inflator as a gas generator and constructed so that the airbag may be expanded and deployed toward the occupant by the gas the inflator generates upon impingement of the vehicle, thereby receiving the occupant""s body.
With the recent demand of a more lightweight vehicle, the airbag device is required to be compactified. The more compactified the casing, however, the more difficult becomes the work of assembling the airbag in the casing. In particular, with a conventional typical airbag device, a rectangular lip portion of the airbag is fixed to the inside wall of the opening marginal portion of the casing with a bag retainer, etc. and hence, the smaller the open area of the casing is made, the more difficult the work of fixing the airbag to the casing.
Conventional airbag devices are classified, according to the way of arrangement of housing the inflator and airbag in the casing, into a series arrangement type as shown in FIG. 13 and a parallel arrangement type as shown in FIG. 14.
In the series arrangement type of airbag device as illustrated in FIG. 13, in a casing 101 opening upwards there are housed and disposed a columnar inflator 102 at its bottom side and an airbag 103, at its upper opening side. Since the airbag 103 and the inflator 102 are arranged upwards and downwards, it is possible to make the opening area of the casing 101 small, but the entirety of the airbag 103 is forced out by the gas given off from the inflator 102 and yet controlling its deployment behavior is not easy.
According to the parallel arrangement type of airbag device shown in FIG. 14, in the casing 101 opening upwardly, the columnar inflator 102 is arranged at the frontward side of the vehicle, namely counter-occupant side whereas the airbag 103 is housed at the rearward side of the vehicle, namely the occupant side. In this case, the inflator 102 and the airbag 103 are arranged fore and aft, so that it is possible to deploy the airbag from its upper side by the gas generated from the inflator 102. However, a door covering the opening of the casing 101 is indispensably large because of a large opening area of the casing 101 and thus there are many restrictions in mounting on the vehicle.
Another arrangement type of one is also proposed as shown in FIG. 15, wherein the casing 101 opening upwardly is provided, at its central part relative to the fore-and-aft direction, with a concave portion 104 on which to dispose the inflator 102, a diffuser 105 is provided so as to cover the inflator 102 arranged within the concave portion 104, and the airbag 103 is folded and accommodated fore and aft relative to the diffuser 105. With this type, because the inflator 102 is arranged in the center, it is difficult to control the deployment behavior of the airbag 103 and besides owing to a large opening area of the casing 101 the door covering the opening is also large, which causes many restrictions in mounting on the vehicle.
Aside from above, another type of airbag device is also known in the art, which is constructed so that a diffuser for adjusting and regulating the gas flows generated by the inflator is formed in a cylindrical form to surround the outer circumference of the inflator in order to facilitate the work of securing the airbag to the casing and arranged within the lip portion of the airbag thereby to engage the airbag with the diffuser within the casing.
FIG. 16 is a sectional view of a prior art airbag device of this kind. In a casing 201, a generally columnar inflator 202 and a folded airbag 203 are accommodated. The inflator 202 is loaded in a columnar diffuser 204 and locked through a cap 205 to the one of opposed sidewalls of the casing 201 by means of a bolt 206 and nut 207. The airbag 203 is attached at its lip portion 208 to wrap the outer circumference of the diffuser 204, thereby being engaged within the casing 201. The airbag 203 has right-hand and left-hand openings whose marginal portions 209, 210 are pinched in clearances X between the edges of the diffuser 204 and the sidewalls of the casing 201, which are in turn made small by the locking of the inflator 202 with the aid of the bolt 206 and nut 207 to prevent the gas from leaking.
With the construction shown in FIG. 16, however, the gas from a gas blowoff part 211 provided at one end of the inflator 202 is directly blown to the clearance X, so that it is difficult to avoid firmly the gas leakage.
FIG. 17 is a sectional view showing another known airbag device of this kind. Here, the opening marginal portions 209, 210 of the airbag 203 are not pinched in the clearances X between the diffuser 204 and the sidewalls of the casing 201, but the clearances X are closed by pressing the edge of the diffuser 204 with the cap 205.
However also in this construction shown in FIG. 17, the gas is likely to leak as a result of deformation of the end of the diffuser 204 owing to a gas pressure from the gas blowoff part 211. Furthermore since the opening marginal portion 209 of the airbag 203 is not pinched, the gas is likely to leak also from a clearance between the opening margin 209 and the perimeter of the diffuser 204.
In view of the prior art problems and difficulties described above, this invention has been made and therefore a first object of this invention is to provide an airbag device, with which it is easy to control the deployment behavior of the airbag and which is superior in workability in assembling the airbag in the casing.
A second object of this invention is to prevent the inflator gas from leaking outside, in an airbag device such that the airbag is engaged within the casing with a cylindrical member such as a diffuser in order to improve the workability of assembling the airbag in the casing.
A first invention for solving the first object is an airbag device comprising a casing having an opening, a generally columnar inflator housed in the casing at its bottom side, an airbag folded and housed in the casing at its opening side and a cylindrical member surrounding the outer periphery of the inflator and having at its peripheral surface holes for blowing off gas emitted by the inflator, wherein the cylindrical member is provided with a partition wall projecting toward the opening side of the casing to compart the space for housing therein the airbag into two sides, the airbag is divided and housed in the one side and the other side of the partition wall, the airbag has a lip portion extending to the bottom part of the cylindrical member so that the outer periphery of the cylindrical member is surrounded by the airbag, the bottom part of the cylindrical member is locked to the bottom surface of the casing to form a locked part, with which the lip portion of the airbag is engaged to fix the airbag to the casing.
According to this airbag device, the bottom part of the cylindrical member is locked to the bottom surface of the casing in the state that the cylindrical member is arranged inside the lip portion of the airbag, whereby it is possible to fix the airbag on the bottom surface of the casing. Consequently, the airbag device is excellent in the workability of assembling the airbag and the cylindrical member in the casing and advantageous particularly in case where the opening area of the casing is small.
This airbag device falls under a series arrangement type wherein the airbag and the inflator are arranged upwards and downwards in the casing, and hence the opening area of the casing can be made small. Moreover the diffuser for controlling the gas flow to the airbag is provided with the partition wall, by which the airbag is divided into two and housed and hence, it is possible to control the deployment behavior of the airbag despite a series arrangement type.
Thus the abovementioned airbag device is compact, yet the deployment behavior of the airbag can be controlled easily and an excellent workability of assembling the airbag in the casing is achieved.
In the airbag device of this invention, the cylindrical member may be provided at its bottom part with a locking projection and the lip portion of the airbag and the bottom surface of the casing may be formed with through-holes through which to insert the locking projection, in order that the locking projection of the cylindrical member is inserted into the through-hole of the airbag, and further into the through-hole of the casing thus engaging both, thereby fixing the bottom part of the cylindrical member to the bottom surface of the casing.
In this case, the airbag can be assembled in the casing in the state that the airbag is locked to the cylindrical member by catching the lip portion of the airbag on the locking projection of the cylindrical member. With the airbag thus assembled, the lip portion is engaged with the locking projection of the cylindrical member.
In the airbag device of this invention, it is preferred that the casing be open nearly upwards and arranged within an instrument panel of a vehicle so that the axial direction of the inflator is oriented in the width direction of the vehicle, the space for housing therein the airbag be comparted for and aft by the partition wall of the cylindrical member and the airbag be divided and housed into a frontward side and a rearward side of the vehicle relative to the partition wall in a folded state, the folded part of an upper bag in a deployed form of the airbag be housed in the frontward side of the vehicle relative to the partition wall while the folded part of a lower bag in a deployed form of the airbag be housed in the rearward side, and the holes on the peripheral surface of the cylindrical member be arranged so that the opening area of the part of holes located at the frontward side of the partition wall is larger than the opening area of the part of holes located at the rearward side of the partition wall.
By that construction, it is possible to blow out more gas from the frontward side of the partition wall to deploy rapidly the folded part of the upper bag followed by deploying rapidly the folded part of the lower bag and to control the deployment behaviors of the airbag.
Here, the holes of the peripheral surface of the cylindrical member may be provided only at the frontward side of the vehicle relative to the partition wall, whereby it is possible to achieve more rapidly the deployment of the upper bag housed in the frontward side.
In this embodiment, it is further preferred that the upper bag of the airbag be folded in a bellows form and the lower bag in a roll form. Then it is possible to achieve a more rapid deployment of the upper bag.
A second invention for solving the second object consists in an airbag device comprising an airbag, an inflator assuming a generally columnar form and having at its axially end a gas blowoff part, a casing housing therein the airbag and the inflator and having an opening through which to expand out the airbag, and a cylindrical member surrounding the outer circumference of the inflator and having at its peripheral surface holes for blowing off gas emitted from the inflator into the airbag, wherein the cylindrical member is disposed within a lip portion of the airbag and arranged between a first sidewall and a second sidewall of the casing opposed to each other, the inflator loaded in the cylindrical member is locked, at its one end constituting a gas blowoff part, to the first sidewall and, at its other end, to the second sidewall, the airbag is engaged within the casing with the cylindrical member arranged inside it, the gas blowoff part of the inflator is covered with a gas-restraining wall projecting from the first sidewall between the gas blowoff part and the cylindrical member.
In the second airbag device, at the one end of the inflator having the gas blowoff part, the gas-restraining wall is provided in a manner projecting from the first sidewall of the casing thereby covering the radial outside of the gas blowoff part. On account of this, the gas blown out radially outwardly is prevented from blowing directly to the clearance between the first sidewall of the casing and the edge surface of the cylindrical member. Therefore gas leakage out of the clearance can be avoided.
Because of the gas-restraining wall it is possible to suppress that the end of the cylindrical member deforms owing to the pressure of gas blown out radially outwardly from the gas blowoff part and the gas leakage is diminished.
Furthermore where the lip portion of the airbag has openings for securing both ends of the inflator to the sidewalls of the casing and marginal portions around the openings are pinched between the sidewalls of the casing and the edge surfaces of the cylindrical member, it is possible to protect the opening marginal portions of the airbag from the heat of the gas by means of the gas-restraining wall.
When the cylindrical member is subjected to a force of shifting it in the deploying direction by the deployment of the airbag, the gas-retraining wall provided within the cylindrical member can suppress the shifting.
By the gas-restraining wall, it is additionally possible to change the flow of the gas blown off in radial directions out of the gas blowoff part, thereby to flow the gas along the axial direction of the inflator. Because of this it is possible to adjust the gas flows blown off from the holes of the peripheral surface of the cylindrical member so that the gas flows are equalized in the axial direction of the inflator and hence, the control of deployment of the airbag can be advantageously performed.
The gas-restraining wall is not limited to that in the aforementioned example, which is provided in the entire periphery of the gas blowoff part. For example, the gas-restraining wall may be provided only in nearly a half area the opening area of the casing in the peripheral direction of the gas blowoff part. From the viewpoints of suppressing the deformation of the casing and cylindrical member upon deployment of the airbag and exhibiting the aforementioned effect more sufficiently, it is preferred to provide the gas-restraining wall over the circumferentially entire area of the gas blowoff part.
It is preferred that the gas-restraining wall project in a manner covering more than a half the gas blowoff part in the axial direction. In other words, the gas-restraining wall is preferred to project to cover more than half the axial opening area for a plurality of gas blowoff outlets provided on the peripheral surface of the gas blowoff part. More preferably, the gas-restraining wall projects to cover the axial entirety of the gas blowoff part, from the aspect of exhibiting the aforementioned effects more sufficiently.
The gas-restraining wall may be provided either as the first sidewall itself of the casing or separately from it. In case where it is separately provided, for example, a circular opening is formed in the first sidewall, and the inflator is attached at its one end to close the opening and secured to the sidewall through a cap, to which the gas-restraining wall may be provided.
In the second airbag device, the lip portion of the airbag may be provided with openings for securing both ends of the inflator to corresponding sidewalls of the casing, the marginal portion around the opening being pinched between the gas-restraining wall and the cylindrical member. In this case, it is possible to suppress effectively the gas leakage from the clearance between the cylindrical member and the first sidewall of the casing and concurrently to protect the opening marginal portion of the airbag from the heat of gas.
In accordance with this invention, it is more effective to combine the construction of the first airbag device and the construction of the second airbag device in performing the deployment control of the airbag. Stated another way, by combining both constructions, more particularly, the partition wall and the gas-restraining wall which are concerned with the deployment control of the airbag, the gas flows blown out of the cylindrical member can be adjusted so as to be equalized in the axial direction of the inflator and the resulting adjusted gas flows can be supplied to the airbag divided by the partition wall extending in the axial direction of the inflator and housed in a folded state, so that a more effective deployment control of the airbag is possible.